In magnetic recording systems for data storage, a thin-film magnetic head has been put to practical use in order to realize a high transfer rate and a high recording density. Use of such a thin-film magnetic head as a multitrack fixed head is suitable for the attainment of a higher transfer rate especially in recording systems employing a magnetic tape as the recording medium. This is because thin-film magnetic heads can be easily fabricated into multitrack heads. A desirable reproducing head is a high-output magneto-resistive head (MR head).
On the other hand, magnetic metal particles superior to magnetic iron oxide and CrO.sub.2 in electromagnetic characteristics are suitable for use as the magnetic particles of a magnetic recording medium. The binder resin used for dispersing magnetic particles therein is desirably a vinyl chloride resin from the standpoints of dispersing ability and storage stability.
However, there is a problem that vinyl chloride resins generate hydrogen chloride, which corrodes thin-film magnetic heads. This problem has been an obstacle to the use of vinyl chloride resins. Even the vinyl chloride resins designed not to generate hydrogen chloride, e.g., "MR-110", manufactured by Nippon Zeon Co., Ltd., Japan and containing epoxy groups within the molecule, have been insufficient.
In JP-B-6-42283 (the term "JP-B" as used herein means an "examined Japanese patent publication") is disclosed a combination of a magnetic recording medium containing a binder consisting mainly of not a vinyl chloride resin but a polyurethane and a thin-film MR head ("Drive F613A", manufactured by Fujitsu Ltd., Japan). However, since the polyurethane is inferior in dispersing ability to vinyl chloride resins, the magnetic layer has a rough surface undesirable in high-recording-density media. Another drawback is that the polyurethane hydrolyzes with the lapse of time to cause head fouling, namely, the conventional magnetic recording medium has insufficient storage stability.
It was thus found that the polyurethane is also unsuitable for use as the binder resin of a magnetic recording medium to be used in combination with a thin-film magnetic head for realizing a high transfer rate and a high recording density. A technique for preventing head fouling and corrosion has been strongly demanded in such a magnetic recording system employing a combination of a thin-film magnetic head and a magnetic recording medium.